The objective of the project is to further our understanding of mating behavior in Norway rats and other mammals. The project focuses on pheromonal sex attractants as mediators of the initial step in the mating sequence of many animals; i.e., locating a suitable sex partner from a distance. The proposed experiments involve the use of a new technique to answer the question: What role does previous experience play in the control of behavior mediated by sex attractants in rats? A preliminary experiment revealed that heterosexually have more rats which later prove to be sexually vigorous prefer the bodily cues from receptive anesthetized females over those from nonreceptive anesthetized females, thus, raising interesting questions concerning the ontogeny of the preference. The results of earlier research raise the same questions concerning the ontogeny of the preference by sexually naive females for the bodily cues from intact adult meals over those from castrated adult males. In one experiment, we will test the hypothesis that the preference by naive males for receptive over nonreceptive anesthetized females stems, via a process analogous to imprinting, from the males' exposure to their dam's post-partum estrus or from their exposure to the odors from cycling females after the males are weaned. In a second experiment, we will test a similar hypothesis that might account forthe preference by naive females for intact over castrated anesthetized males. In a third experiment, we will determine whether castration influences the responses of sexually experienced males to receptive and nonreceptive anesthetized females.